In my thesis I made use of the standard Drexel Dissertaion style file
drexel-thesis.cls including deluxetable and lots of other examples in this
DissertationDocs repo. The yahapj.bst file makes it so the references are
properly hyperlinked to their ads/arXiv pages. But for the general purpose of
the reference style, I used ieeetr style.
In addition to my thesis I have also included my presentation slides. These
were also made in latex (using beamer), and in them I made heavy use of tikz, a
package that allows you to annotate basic shapes onto the slides. The commented
\draw[help lines,xstep=.1,ystep=.1] (0,0) grid (1,1); lines will draw a
series of grid lines on the slide to help with positioning. I only included one
working example of the presentation with a few slides, which works as a
demonstration of how to use beamer to generate presentation slides if you are
interested in. However, I have my major slides built by Powerpoint which is not
included in this repo.
Semiconductor nanowires have been used in a variety of passive and active
optoelectronic devices including waveguides, photodetectors, solar cells, LEDs,
Lasers, sensors, and optical antennas. We examine GaAs/AlGaAs core-shell
nanowires (CSNWs) grown on both GaAs and Si substrates by vapor-liquid-solid
(VLS) method followed by Metal-Organic Chemical Vapor Deposition (MOCVD). These
nanowires show extremely enhanced optical properties in terms of absorption,
guiding, radiation of light, and even lasing. For the wavelength range of
700-1200nm these core-shells which only occupy~15% of the volume compared to
thin films of the same height, reflect 2-4% of light for the CSNWs grown on
Si, and 3-7% of light for those grown on GaAs substrate. The photoluminescence
(PL) spectrum shows 923 times more light emitted from CSNWs grown on GaAs
compared to bulk GaAs at room temperature, and optical pumped lasing with
threshold of around
Analysis of the interaction of light with cylindrical and hexagonal structures with sub-wavelength diameters identifies both transverse and longitudinal plane modes which we generalize to volumetric resonant modes, importantly, without the need for vertical structures such as Bragg mirrors commonly used in vertical cavity surface emitting lasers (VCSEL's). We report on FDTD simulations with the aim of identifying the dependence of these modes on geometry (length, width), tapering, shape (cylindrical, hexagonal), core-shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how NWs form excellent optical cavities without the need for top and bottom mirrors.
However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption) and downward transitions (emission) of light in nanowires, rather, the electronic transition rates should be considered. Using Fermi's Golden Rule in interaction of light and matter, we discuss how the transition rates change due to electronic wave function and identify three factors, namely, oscillator strength, overlap functions, and the joint optical density of states(JDOS), explicitly contributing to the transition rates with strong dependence on dimensionality.
We apply these results to the study of lasing in as-grown CSNW on Si & GaAs
and discuss how these subwavelength structures can have enhanced optical gain,
quantum efficiency and 175 times more optical output power compared to their
bulk counterparts despite their large